Drilling methods and apparatus employing out-of-phase pressure variations in a drilling fluid



DRILLING METHODS AND APPARATUS EMPLOYING OUT-OF-PHASE PRESSURE VARIATIONS IN A DRILLING FLUID Filed Aug. 5. 1966 April 1969 E. M. GALLE ETAL 3,441,094

United States Patent US. Cl. 175-56 16 Claims ABSTRACT OF THE DISCLOSURE Following is disclosed methods and apparatus for drilling bore holes in the earth wherein out-of-phase pressure variations are generated in the fluid surrounding the drill bit and in the fluid upstream of the nozzles in the bit to cyclically and simultaneously reduce bottom hole pressure, increase jet velocity, and increase bit loading to increase the drilling rate.

This application is a continuation-in-part of a copending application Serial No. 379,257, filed June 30, 1964, now abandoned in favor of Serial No. 552,788, filed May 25, 1966, now Patent No. 3,405,770.

In the above-mentioned patent, we disclose methods and apparatus which utilize pressure variations to cyclically reduce bottom hole pressure, increase jet velocity, and increase the bit loading to increase the drilling rate. In the above patent, however, our methods and apparatus utilize pressure variations which are intentionally transmitted only to the cavity which surrounds the drill bit. In our present application we will disclose methods and apparatus by which pressure variations are transmitted to the exterior cavity surrounding the bit in a manner similar to that described in the above patent, and in which pressure variations are also transmitted in an interior cavity immediately above the drill bit nozzles. Such pressure variations when induced in the drilling fluid exterior and interior of a drill bit may be effectively used to decrease bottom hole pressure, increase jet velocity and increase bit loading.

It is, accordingly, the general object of our invention to provide drilling methods and apparatus in which pressure variations in addition to those which may be induced in the drilling fluid exterior of the drill bit are utilized to increase jet velocity and increase the drilling rate.

Another object of our invention is to provide drilling methods and apparatus in which the entire drilling fluid passing downwardly through the drill string members may be utilized to generate pressure variations at the bottom of a bore hole to cyclically reduce bottom hole pressure, increase jet velocity and increase bit loading.

Another object of our invention is to provide apparatus which is particularly elfective in producing pressure variations or acoustic vibrations substantially out-of-phase with each other in a cavity surrounding the drill bit and in a cavity immediately above the drill bit nozzles to simultaneously and cyclically reduce bottom hole pressure, increase jet velocity and increase bit loading.

A broad concept of our invention is to utilize an acoustic vibration generator, preferably of the fluidic oscillator type, in a lower region of the drill string to generate acoustic vibrations in an interior cavity immediately above the bit nozzles. These acoustic vibrations cyclically increase and decrease the jet velocity of the fluid flowing through the nozzles of the drill bit, but due to the high impedance of the drill bit nozzles, only a small percentage of the pressure variation induced in this cavity reaches 3,441,094 Patented Apr. 29, 1969 lator in another acoustic cavity exterior of and surround- \a ing the drill bit and these acoustic vibrations are preferably out-of-phase with the acoustic vibrations induced in the interior cavity. This enables the pressure variations generated in the interior and exterior acoustic cavities to cooperate with each other in a manner to greatly increase the variations in jet velocity and thus to significantly increase the drilling rate. In addition to this broad concept, our invention encompasses related concepts and apparatus which will become apparent in the following detailed description.

The above and other objects are efiected by our invention as will be apparent from the following description, taken in accordance with the accompanying drawing, forming a part of this application, in which:

FIG. l-A is a side elevational view, partially in longitudinal section, of a drill bit and apparatus connected therewith which icludes an elastic vibration generator and a coupling device that cooperate to induce pressure variations in the above-mentioned interior and exterior acoustic cavities;

FIG. l-B is a side elevational view in longitudinal section of a tubular carriage which contains two Helmholtz resonators. The lower threaded portion of the apparatus of FIG. 1-B is in operation secured to the upper threaded portion of the apparatus of FIG. l-A;

FIG. 2 is a cross sectional view as seen looking along the line II-II of FIG. l-A;

FIG. 3 is a fragmentary perspective view showing the lower portion of the apparatus of FIG. l-A;

FIG. 4 is a fragmentary side elevational view of a portion of the device of FIG. l-A; and

FIG. 5 is a fragmentary side elevational view in sectliog of a modified form of the apparatus shown in FIG.

F IG. 1-A illustrates apparatus in which a bistable elastic vibration generator A is utilized in generating pressure variations upstream from the drill bit nozzles, and simultaneously in the external cavity surrounding the drill bit, with said pressure variations being substantially 180 out-of-phase.

An acoustic coupling device B is utilized to transmit pressure variations from the elastic vibration generator A to the internal cavity above the bit nozzles and to the cavity around the drill bit. A typical drill bit C is shown connected to the lower end of a housing D. The drill bit C may have standard jet nozzles as shown in the drawing.

The preferred embodiment shown in FIG. 1-A has the upper end of housing D threaded for connection to the apparatus of FIG. 1-B, as indicated by the numeral 11. The elastic vibration generator A is disposed in a carriage 13 disposed inside the upper portion of housing D. Carriage 13 has an upper axial bore 15 which communicates with an axial bore 17 of a fluidic oscillator unit 19. The carriage 13 is divided into two pieces 21, 23 as shown in FIG. 2 so that the fluidic oscillator unit 19 may be conveniently assembled therein. Suitable seal means (not shown) are provided to keep all downwardly flowing fluid passing through a power nozzle 24 of the fluidic oscillator unit 19.

The fluidic oscillator unit 19 may be of the same general type described in our above-mentioned patent in which, however, only a portion of the total available fluid passes through the power nozzle. But in the apparatus of FIG. 1-A, all DC (direct current) flow passes through output leg 25 of the fluidic oscillator while being blocked from passing through the other output leg 27. In the above-mentioned patent there is DC flow through both output legs. Otherwise, fluidic oscillator unit 19 is substantially identical with the fluidic oscillator unit in said patent. For example, feedback loops are defined by passages 29, 31 and 33, 35 which communicate with each other respectively via the axially extending bores or chambers 37, 39 (see especially FIG. 2).

Carriage 13 engages the upper end of a flange 41 having its peripheral surface engaged with and sealed by suitable means against housing D, with the cylindrical body 42 in the coupling device and the inner cylindrical surface of housing D defining an annular cavity 45. Axial cavity 43 communicates with output leg 25 of the oscillater unit while annular cavity 45 communicates with output leg 27. Both output legs communicate with and extend from respective diffuser channels 47, 49 of the fluidic oscillator unit 19 through the carriage 13. Aperture 51 extends through flange 41 to connect output leg 27 with annular cavity 45.

Pressure variations or acoustic vibrations generated in the oscillator unit 19 are transmitted via output leg 25, axial cavity 43 and an axial bore 55 in the lower region of housing D to a cavity inside the bit immediately above the bit nozzles 56. Axial cavity 43, axial bore 55, and the cavity inside the bit constitute a single acoustic cavity, hereinafter called the interior acoustic cavity.

Output leg 27 communicates through aperture 51 with annular cavity 45 and with a plurality of large apertures 59 in housing D that extend to the cavity surrounding the drill bit C. Annular cavity 45, apertures 59 and the cavity surrounding the bit constitute another single acoustic cavity, hereinafter called the exterior acoustic cavity. DC flow through this cavity is prevented by a DC block 61, which in this instance includes a plurality of axially spaced apart flexible members 63 which are annular in configuration and sealingly engage the interior of housing D and the exterior of the cylindrical body 42. Sealing engagement is effected by bonding the inner and outer peripheral edges 64, 66 (see FIG. 4) of each flexible member with two concentric axially extending metal sleeves 67, 69. Seal means 71, 73 may be provided as shown in FIGS. l-A and 4 to prevent fluid flow past the annular sleeves and the mating surfaces of housing D and cylindrical body 42.

In operation of the apparatus described thus far, fluid from the mud pump (not shown) flows down the drill string and through power nozzle 24 of the fluidic oscillator unit, which causes the fluid to flow alternately into diffuser channels 47, 49. The acoustic inertance of diffuser channels 47, 49 and output legs 25, 27 combine respectively with the interior acoustic cavity and the exterior acoustic cavity to form Helmholtz resonators which are resonant at the operating frequency of the fluidic oscillator unit.

The alternate How of fluid into diffuser channels 47, 49 causes large pressure variations in the fluids therein which are essentially 180 out-of-phase in the exterior and interior acoustic cavities. The large pressure variations in these cavities, due to their being out-of-phase, cause large flow variations to occur in the bit nozzles. In effect the operation of the device can be described as a pushpull arrangement operating across the bit nozzle. When the pressure in the exterior acoustic cavity is at a minimum, the pressure in the interior acoustic cavity will be maximum and will effect extremely high jet velocity in conjunction with a minimum bottom hole pressure.

It is preferable that the pressure variations in the fluid in the exterior and interior acoustic cavities be 180 out-of-phase. The beneficial effects of inducing pressure variations in the above cavities begins to be lost and ultimately may disappear as the pressure variations more closely approach an in-phase relationship. Thus, the pressure variations upstream and downstream from the bit nozzles should be as close as practicable to being 180 out-of-phase to maximize effectiveness.

The DC flow block 61 is placed in the annular cavity 45 to prevent DC flow through this cavity and out apertures 59 to the annulus. The DC block in this instance consists of a plurality of flexible members of annular form. These members are typically high strength elastomers of about /8" thickness. Such DC flow blocks must Wihstand the total pressure drop across the bit nozzles and are arranged as shown such that each individual member takes a proportionate share of the total pressure differential across the bit nozzles. In addition to each member being strong enough to take its proportionate share of the pressure drop across the nozzles, it must also be very resilient such that it offers negligible impedance to passage of acoustical signals. One or more drilled holes 77 in sleeve 69 (see FIG. 4), sealed with plugs 79, are provided between each pair of flexible members 63 such that the spaces therebetween may be purged of air and completely filled with a suitable liquid such that each member will be equally elongated when the DC block is subjected to a pressure drop across the bit nozzles.

In a push-pull arrangement as shown in FIG. 1 and assuming the pressure variations in the interior acoustic cavity and the exterior acoustic cavity are essentially equal and 180 out-of-phase, back flow through the nozzles will occur whenever the peak variation in the pressure in each of these cavities exceeds one half of the average pressure drop across the bit nozzles. Backfiow of large magnitude is undesirable in that it is not beneficial in cleaning bottom but does dissipate considerable power. If peak pressure variations in the exterior acoustic cavity of a magnitude greater than one half the average pressure drop across the bit nozzles are desired, backflow may still be avoided if the apparatus is designed such that the sum of the peak pressures in the interior and exterior acoustic cavities never exceeds the average pressure drop across the bit. This may be accomplished by making the interior acoustic cavity appreciably larger than the exterior acoustic cavity and using appropriate inertances in association with each of the these cavities such that they are resonant at the operating frequency.

As previously mentioned, the DC flow through the output legs of oscillator unit 19 is unbalanced due to the DC block in annular cavity 45. If it is desired to design the device such that the fiuidic oscillator unit 19 operates in a balanced mode, a one half wavelength line 81 (see FIG. 5) may be connected between the upper region of annular cavity 45 through cylindrical body 42 into axial cavity 43 to effect acoustic isolation between the above described interior or exterior cavities, while permitting DC flow from upper region of cavity 45 into axial cvaity 43. The diameter of the half wavelength line should be as small as possible without causing a high DC flow pressure drop along the line.

To decrease or eliminate the power loss up the annulus, a Helmholtz resonator 83 (see FIG. l-B) of a tubular carrier 84 is positioned with its entrance 85 located M1 wavelength above the cavity surrounding the bit, as is explained in our above-mentioned patent. Also, it may be advantageous to provide another Helmholtz resonator 87 with its entrance 89 communicating with the axial bore 91 a half wave length above power nozzle 24 of the oscillator unit 19 to prevent power dissipation upwardly through the fluid passing through the drill string members. It is also preferable that a shock absorber or high compliance drill string member be positioned one half wavelength in the steel above the drill bit.

An example of manufacturing data that may be used to construct the apparatus of FIG. 1 which may be used in 7% holes and which is designed to operate at about cycles per second is as follows:

Some of the manufacturing data for the device will be provided by giving the acoustical element values rather than by giving physical dimensions of the various passages and cavities. The physical dimensions of the pitssageways and volumes of the acoustical elements may be calculated by the formulas given in the above-mentioned patent.

The elastic vibration generator unit 19 receives all the drilling fluid pumped by mud pump (not shown) and therefore must be somewhat larger than the similar unit specified in the above-mentioned patent. All oscillator unit dimensions described in the copending application will be the same with the exception of the depth of the passageways, which should be increased in direct proportion to the desired increase in the flow rate of the drilling fluid in this oscillator as compared to the device of the copending application. The combined inertance of oscillator diffuser channel 47 and aperture 25 may be 41.6 lbs. secF/ft. and the compliance of interior acoustic cavity 1.0 10- ft. /lbs. The combined inertance of diffuser channel 49 and aperture 27 may be 210 lbs. secF/ft. and the compliance of exterior acoustic cavity 1.32 1() ftfi/lbs. The acoustical compliance of the DC flow block 61 in exterior acoustic cavity may be 5.76 lft. /lbs. The apertures 59 should be made with as large a diameter as possible and as numerous as possible consistent with structural strength of the housing D and as short as possible such that the inductance of these apertures will be negligible. The average impedance of the bit nozzles may be .22X 10 lbs. sec./'ft. Exterior and interior acoustic cavities should preferably be wavelength or less in axial length.

While we have shown our invention in only two of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof. Our invention is not limited to the specific forms of the apparatus shown, nor to specific methods of constructing such apparatus. It is not essential, for example, that all the drilling fluid pass through the fluidic oscillator unit. The various materials which may be successfully utilized and the geometric form of the fluidic oscillator and coupling devices may vary widely. The frequency and amplitude of the pressure variations may vary widely and the broad concepts of our invention are not limited thereby. However, practical limitations are present since the size of the acoustical components is controlled by especially the frequency. Suitable ranges for the frequencies and amplitudes of the pressure variations may be seen in the above mentioned copending applications.

We claim:

1. In the rotary method of well drilling with a drill bit including nozzle means, the improvement comprising inducing elastic vibrations in the drilling fluid in a cavity surrounding the drill bit while simultaneously inducing elastic vibrations in the drilling fluid in another cavity immediately upstream of the nozzle means, said elastic vibrations being substantially 180 out-of-phase.

2. The method of claim 1 wherein the frequency of the elastic vibrations lies in a band of from about 30 to 1000 cycles per second.

3. In the rotary method of well drilling with a drilling bit including nozzle means, the improvement comprising transmitting substantially the entirety of the drilling fluid from a mud pump through a fluidic oscillator type elastic vibration generator having two output legs; acoustically coupling one output leg with a cavity immediately above the drill bit nozzle means; acoustically coupling the other output leg with another cavity including the exterior of the drill bit; said cavities being substantially acoustically isolated from each other, with the resulting elastic vibrations in said cavities being substantially 180 out-of-phase.

4. The method of claim 3 wherein the frequency of the elastic vibrations lies in a band of from about 30 to 1000 cycles per second.

5. Apparatus for increasing drilling rates in rotary well drilling which includes a drill bit having nozzle means, said apparatus comprising: a housing adapted for insertion into a drill string; an elastic vibration generator carried by said housing and having two output legs secured in an upper region of said housing; an acoustic coupler in said housing that defines a cavity immediately above the drill bit nozzle means and another cavity having a portion thereof surrounding the drill bit; a DC fluid flow block disposed in the acoustic coupler to prevent DC flow to the cavity having a portion thereof surrounding the drill bit, with the elastic vibrations in the two output legs of the elastic vibration generator and in said two acoustic cavities being substantially out-of-phase.

6. The apparatus defined by claim 5 wherein the frequency of the elastic vibration generator resides in a range varying from about 30 to 1000 cycles per second.

7. The apparatus defined by claim 5 wherein said DC flow block comprises a plurality of flexible, impervious elements that span a transverse area of the associated cavity and are bonded to walls partially defining said cavity; and means carried by a selected one of said walls for filling the spaces between the elements with a liquid.

8. The invention defined by claim 5 wherein the two cavities are connected with a one-half wave length delay line which permits DC flow between the cavities while acoustically insulating the cavities.

9. In the rotary method of well drilling with a drill bit including nozzle means, the improvement comprising inducing elastic vibrations in the drilling fluid in a cavity surrounding the drill bit while simultaneously inducing elastic vibrations in the drilling fluid in another cavity upstream from the nozzle means, said elastic vibrations being substantially out-of-phase.

10. The method of claim 9 wherein the frequency of the elastic vibrations lies in a band of from about 30 to 1000 cycles per second.

11. In the rotary method of well drilling with a drill bit including nozzle means, the improvement comprising transmitting substantially the entirety of the drilling fluid from a mud pump through a fluidic oscillator type elastic vibration generator having two output legs; acoustically coupling one output leg with a cavity immediately above the drill bit nozzle means; acoustically coupling the other output leg with another cavity including the exterior of the drill bit; said cvaities being acoustically insulated from each other, with the resulting elastic vibrations in said cavities being substantially out-o-f-phase.

12. The method of claim 11 wherein the frequency of the elastic vibrations lies in a band of from about 30 to 1000 cycles per second.

13. Apparatus for increasing drilling rates in rotary well drilling with a drill bit including nozzle means, said apparatus comprising: a housing adapted for insertion into a drill string; an elastic vibration generator carried by said housing and having two output legs secured in an upper region of said housing; an acoustic coupler in said housing that defines a cavity immediately above the drill bit and another cavity having a portion thereof surrounding the drill bit; a DC fluid flow block disposed in the acoustic coupler to prevent DC flow to the cavity having a portion thereof surrounding the drill bit, with the elastic vibrations in the two output legs of the elastic vibration generator and in said two acoustic cavities being substantially out-of-phase.

14. The apparatus defined by claim 13 wherein the frequency of the elastic vibration generator resides in a range varying from about 30 to 1000 cycles per second.

15. The apparatus defined by claim 13 wherein said DC flow block comprises a plurality of flexible, impervious elements that span a transverse area of the associated cavity and are bonded to walls partially defining said cavity; and means carried 'by a selected one of said walls for filling the spaces between the elements with a liquid.

16. The invention defined by claim 13 wherein the two cavities are connected with a one half wave length delay 7 8 line which permits DC flow between the cavities while 3,094,176 6/1963 Cook 17556 X acousticallyinsulatingthe cavities. 3,163,240 12/1964 Bodine 175-56 3,216,514 11/1965 Nelson 175-56 References Cited 3,251,424 5/1966 Brooks 175-56 UNITED STA TES PATENTS 5 CHARLES E. OCONNELL, Primary Examiner. 2,554,005 5/1951 Bodine 175-55 2 72 322 3 1954 Bodine 175 5 RICHARD E.FAVREAU,AsszstantExammer. 2,824,718 2/1958 Currie 17556 U5, ()1, X R 2,946,565 7/1960 Williams l7556 X 175 57 2,970,660 2/1961 Bodine l7556 X 10 

